Michael R. Bloomberg, the billionaire former mayor of New York City, spent at least $30 million on Friday for a single week of television ads, a show of financial force that signals his willingness to use his vast personal fortune to reshape the Democratic presidential race.
The 60-second biographical commercials will begin on Monday in more than two dozen states and roughly 100 news media markets from California to Maine, a preview of a 2020 campaign budget that could easily stretch into the nine-figure range.
The scope of Mr. Bloomberg’s ad buy is staggering. It is more than all of Mr. Bloomberg’s potential rivals — other than the other billionaire running, Tom Steyer — have spent on television ads all year, and about double what Senator Cory Booker had raised in donations from February through the end of September.
“Mike is prepared to spend what it takes to defeat Donald Trump,” said Howard Wolfson, a top adviser to Mr. Bloomberg, whose formal announcement of his candidacy appears imminent.
Rivals were quick to condemn Mr. Bloomberg, 77, for leveraging his personal fortune to sway the race.
“I’m disgusted by the idea that Michael Bloomberg or any other billionaire thinks they can circumvent the political process and spend tens of millions of dollars to buy our elections,” Senator Bernie Sanders of Vermont said.
The new television campaign provides a hint of how Mr. Bloomberg will focus his resources beyond the early voting states. He will spend $1.6 million in New York City, $1.5 million in Los Angeles, $1.2 million in Houston, $1.1 million in Miami and $794,000 in Boston in an eight-day period, according to Advertising Analytics, a media-tracking company. And more reservations were still arriving late Friday.
Mr. Bloomberg was not overlooking smaller states, either. He had booked $52,000 in ads, for instance, in Fargo, N.D. and $59,000 in Biloxi, Miss.
Mr. Bloomberg has not officially announced he is running for president, though this week he filed a formal “statement of candidacy” with the Federal Election Commission. He had previously filed to be on the ballot in three states.
His expected entry has injected a new element of uncertainty into the race, highlighting its fluidity as well as the angst among many moderate Democrats that the field has moved too far left, and that former Vice President Joseph R. Biden Jr., despite leading in most national polls, is poorly positioned to win. It has also stirred a debate among Democrats about the role of wealth in the primary and accusations from progressive rivals that Mr. Bloomberg is trying to buy the presidency.
“Swell,” Steve Bullock, the governor of Montana who is running a shoestring campaign for president, wrote on Twitter Friday. “Another Billionaire who thinks the Democratic nomination is for sale.”
Campaigning in New Hampshire, Senator Amy Klobuchar of Minnesota joked that she would also be announcing a multimillion ad buy.
“No, I’m not,” she said, with a laugh. More seriously, Ms. Klobuchar argued that Mr. Bloomberg’s wealth could turn off some primary voters, who are tired of big money in politics. “They are tired of all the money in our world that’s at the top and I don’t think they want that at the top of our country,” she said.
The ad buy is the latest in a series of steps that Mr. Bloomberg, who has flirted with past presidential runs but has always demurred, has taken before formally declaring his bid.
He has filed to be on the ballot in Arkansas, Alabama and Texas. He announced a $100 million digital ad campaign against President Trump this month and launched a $15 million voter registration drive. And he went to a predominantly black church last Sunday and apologized for his long embrace of stop-and-frisk police tactics that disproportionately impacted blacks and Latinos during his mayoralty.
“I was wrong,” Mr. Bloomberg said, in a speech that has been his only public remarks since he re-emerged as a possible presidential candidate. “And I am sorry.”
On television, Mr. Bloomberg’s ads are slated to run from the early 5 a.m. local newscasts through the late-night shows, and on almost everything in between, including on prime time programming and major sporting events, according to documents filed with the Federal Communications Commission.
His first ad will be a biographical spot, according to a person familiar with the ad but is not authorized to discuss it publicly.
Mr. Bloomberg has reserved at least $100,000 in time in 56 different news media markets, as of late Friday, from November 25 through December 3, according to Advertising Analytics. In Los Angeles, Mr. Bloomberg was slated to pay $114,000 for four 60-second ads on The Voice, NBC’s popular show, F.C.C. records show.
Bill Knapp, who produced ads for Mr. Bloomberg’s three mayoral campaigns, took a leave of absence from a leading Democratic consultancy, SKDKnickerbocker, to work for Mr. Bloomberg’s coming campaign, the firm announced on Friday. The firm itself will continue working for Mr. Biden.
Mr. Bloomberg’s advisers have said his campaign would bypass the first four states that will vote in February — Iowa, New Hampshire, Nevada and South Carolina — and focus instead on Super Tuesday in March and beyond, where his personal fortune would give him an advantage.
One of the looming questions of the expected Bloomberg candidacy is whether he would actually campaign much in person, or instead lean heavily on paid advertising.
A moderate who first ran for mayor as a Republican and then as an independent and is now plotting a run for president as a Democrat, Mr. Bloomberg could shake up the 2020 primary by offering a centrist alternative to Mr. Biden. And with voluminous spending, he can crowd the airwaves so much that other campaigns cannot break through.
Mr. Steyer, the race’s other billionaire, entered the contest in July and had spent nearly $50 million by the end of September. But Mr. Steyer has taken a completely different approach, airing ads so far mostly in the early primary states, and on cable nationally.
Mr. Bloomberg, with an estimated net worth of more than $50 billion, is one of the wealthiest people in America, with a fortune that dwarfs even Mr. Steyer’s.
Still, waiting to compete until the March contests is a deeply risky gambit for Mr. Bloomberg; many past nominating contests have been all-but-settled after the first four states. Mr. Bloomberg has not registered as a serious contender in any Democratic primary polls conducted since he signaled he would enter the race.
While the March primary states were the overwhelming focus of Mr. Bloomberg’s ad buy on Friday, he also was making some reservations in states, such as New York and Pennsylvania, that will vote later in the calendar.
Paul Winn, a veteran media buyer, called the Bloomberg ad buy “unprecedented.”
“The only media campaigns of comparable size and scope are general election presidential campaigns,” he said.
Lisa Lerer contributed reporting from Hennepin, N.H.